1. Field of the Invention
The present invention relates to a particle and a photoacoustic imaging method using the particle.
2. Description of the Related Art
A photoacoustic imaging method of visualizing in vivo information has been known. The photoacoustic imaging method is a method involving measuring the intensity and generation position of a photoacoustic signal, which is emitted from a specimen through the irradiation of the specimen with light, to obtain the image of a substance distribution in the specimen. The light with which the specimen is irradiated is preferably near infrared light as light having a wavelength of 700 to 900 nm that easily permeates a living body.
It has been known that the irradiation of a Resovist (trademark) (contrast agent for MRI containing an iron oxide particle) with light produces an acoustic wave (2006 IEEE Ultrasonics Symposium p. 393-396). Therefore, there is a possibility that the Resovist (trademark) can be used as a contrast agent for photoacoustic imaging.
Here, the contrast agent for photoacoustic imaging refers to a contrast agent to be used in the photoacoustic imaging method. The photoacoustic imaging method refers to a method involving measuring the intensity and generation position of an acoustic wave, which is emitted from a specimen such as a living body through the irradiation of the specimen with light, to obtain the image of a substance distribution in the specimen. In the case where the contrast agent for photoacoustic imaging is liable to accumulate in a specific target site in the specimen, when an image is obtained by the photoacoustic imaging method after the specimen has been provided with the contrast agent for photoacoustic imaging, a contrast between the specific target site and any other site in the image increases.
However, the iron oxide particle constituting the Resovist (trademark) absorbs a small quantity of light in a near infrared region and emits a weak photoacoustic signal.